1. Field of the Invention
This invention relates to a control mechanism and method for varying the pitch of a propeller in a fluid medium, such as propellers for use on pumps, boats and aircraft. The variable pitch characteristic also finds utility in mechanisms where the propeller is driven by movement of the fluid medium in which it is immersed. More particularly this invention relates to a hydraulic mechanism for controlling the pitch and to an improved mounting for a variable pitch propeller blade.
2. Description of the Prior Art
There are a number of reasons why it is desirable to vary the pitch of such a propeller. One reason is to permit matching the load imposed by the propeller with the speed-torque characteristics of the drive engine. Another desirable objective is rapid acceleration of the vehicle engine without overloading it. Another advantage of pitch control is to achieve maximum economy under stable state conditions. Most variable pitch propellers, such as those used on aircraft and larger boats, are controlled by a mechanism arranged to respond to external signals either from an automatic or manual control system. Generally, such mechanisms are expensive and are not suitable for applications where low cost and automatic operation are requirements.
Although variable pitch propellers have been available for larger boats and for installations justifying expensive and complicated control systems, practical variable pitch propellers have not been available for small boats and for other installations requiring a low-cost simple pitch-control mechanism. The present invention provides such a simple and low-cost system.